The present invention relates to the manufacture of reinforcing preforms for structural composites, and more particularly to optimizing air flow in the manufacturing process and adjusting the air ejector pressure.
The present invention relates to methods and systems for making rigid three-dimensional reinforcement preforms used in resin transfer molding (RTM) and structural reaction injection molding (SRIM) processes for the manufacture of structural composites. The manufacture and use of structural composite materials is becoming increasingly important today, particularly in components for the automotive industry. Structural composites are lighter in weight than conventional steel or metal components and can result in additional advantages, such as allowing fully automated, highly controllable processes, better part-to-part consistency, reduced waste or scrap, and equivalent or increased component performance.
In general, the structural reinforcing preforms are made from a sprayed chopped material such as glass and carbon fiber, which is held together by a binder and molded into a precise form and shape. The preform in turn is then molded into products, such as composite components (both structural and non-structural) and used in automobiles or other vehicles.
The preform material is chopped and applied along with a powdered binder to a preform screen in a mold using a robotic routine. Positive air flow through the screen holds the chopped material on the screen surface. When the spraying is completed, the mold is closed and the preform is compressed to the desired thickness. Heated air is first drawn through the screen in order to melt the binder. Thereafter, cooled or ambient air is drawn through the preform setting the final shape. Once the preform is completed, it is demolded and transferred to a component mold where the structural component is molded.
Although present automated preform processes and systems have been used to produce satisfactory structural composite products, a need exists to improve the processes and systems, particularly to reduce the cost, increase the output and reliability, and make components of various configurations and thicknesses.
It is an object of the present invention to provide improved systems and processes for making rigid three-dimensional reinforcement preforms for resin transfer molding (RIM) and structural reaction injection molding (SRIM) processes for composite components and products. It is also an object of the present invention to optimize the air flow in the manufacturing process, particularly as to each cell in a multiple cell system.
It is another object of the present invention to prevent air flow during mold closure from disturbing the sprayed materials. It is a still further object of the present invention to allow adjustment of the air ejector pressure, especially to accommodate the spraying of various materials or various amounts of materials at various portions of the mold.
In accordance with these objects, the present invention provides improvements and advantages over known preform processes and systems. In particular, separate air systems are used for each cell or station in a multiple cell preform manufacturing system in order to provide the necessary air flow at each preforming cell. This provides manufacturing uniformity and consistency at each cell of a multiple cell system.
In accordance with another aspect of the present invention, seals are provided to eliminate high velocity air flow through gaps in the tooling as the mold is being closed which could otherwise disturb the sprayed materials. Seals can be provided between the net-edge block and the deposition screen as well as between the consolidation screen and the net-edge blocks.
In addition, the air pressure of the material applicators can be varied and adjusted in order to allow different materials to be processed and different characteristics to be achieved in the preforms. The air ejector pressure can be adjusted by a computer controlled pneumatic proportional valve.